- 0.5 %RH Uncertainty *
- Traceable to NIST
- Based on NIST Proven Two-Pressure Principle
- Generate: RH, DP, FP, PPM, Multipoint Profiles
- Computerized Internal Transducer Calibration
- Computes System Uncertainties in Real Time
- Automatically Applies Enhancement Factors
- No Refrigerants - Thermoelectric Cooling/Heating
- Only 4 square feet of floor space (20" x 30 ")
- Touch-screen control
- USB and Ethernet Interface
- Oil-Less w/Membrane Dryer with Power Strip
Principle of Operation
The "two-pressure" humidity generation process involves saturating air or nitrogen with water vapor at a known temperature and pressure. The saturated high-pressure air flows from the saturator, through a pressure reducing valve, where the air is isothermally reduced to test pressure at test temperature.
Humidity generation by the 1200 does not depend upon measuring the amount of water vapor in the air, but rather is dependent on the measurements of temperature and pressure alone. System precision is determined by temperature and pressure measurement accuracy, and on the constancy of the measurements throughout. When setpoint equilibration has been reached the indications of saturation temperature, saturation pressure, test temperature, and test pressure, are used in the determination of all hygrometric parameters.
Control / Display Screen
The Computer/Control System performs all control functions required for humidity generation, as well as displaying, printing, and storing system parameters in real time. The computer/controller is made up of several main components, each with individual yet cooperative functions. The Computer/Control System utilizes a Windows based computer system that is used to read transducers and temperature sensors; supply digital outputs for control of temperatures, pressures, and mass flow; and control relay outputs for control of system power, heaters, heat pump and circulation pump.
Ultra stable temperatures are attained through solid-state thermoelectric cooling and heating of a circulating fluid that jackets the test chamber and associated humidity generation components. Chamber and saturation temperatures are governed by this medium which is computer controlled at any value between 10 °C and 60 °C using PID (proportional-integral-derivative) algorithms.
Pressure And Flow Control
Pressure control and mass flow control are accomplished through computer actuation of electromechanical valve assemblies. Saturation pressure and mass flow are measured continuously and controlled using PID algorithms similar to those employed in temperature control.
Proper calibration of the temperature sensors and pressure transducer ultimately determines the accuracy of the generator. The system employs an integral programmatic calibration scheme allowing the sensors and transducers to be calibrated while they are electrically connected to the humidity generator. Coefficients for each transducer are calculated by the computer and stored to memory.
Pressure And Flow Control
Pressure control and mass flow control are accomplished through computer actuation of electromechanical valve assemblies. Pressure and flow are measured continuously and controlled using PID algorithms similar to those employed in temperature control.
The test chamber accommodates various solid-state sensors, data loggers, chilled mirror hygrometers, and material samples for environmental testing. The 1200 humidity generating system incorporates a 300 series stainless steel fluid jacketed test chamber, with internal dimensions of 6" x 6" x 6" (152 mm x 152 mm x 152 mm). Access is available through a 1.688" (42 mm) diameter port on the right side for probes, cables, sample tubes, etc.